Spatial normalization of neuroimaging data is a standard step when assessing group effects. As a result of divergent analysis procedures due to different normalization algorithms or templates, not ...all published coordinates refer to the same neuroanatomical region. Specifically, the literature is populated with results in the form of MNI or Talairach coordinates, and their disparity can impede the comparison of results across different studies. This becomes particularly problematic in coordinate-based meta-analyses, wherein coordinate disparity should be corrected to reduce error and facilitate literature reviews. In this study, a quantitative comparison was performed on two corrections, the Brett transform (i.e., “mni2tal”), and the Lancaster transform (i.e., “icbm2tal”). Functional magnetic resonance imaging (fMRI) data acquired during a standard paired associates task indicated that the disparity between MNI and Talairach coordinates was better reduced via the Lancaster transform, as compared to the Brett transform. In addition, an activation likelihood estimation (ALE) meta-analysis of the paired associates literature revealed that a higher degree of concordance was obtained when using the Lancaster transform in the form of fewer, smaller, and more intense clusters. Based on these results, we recommend that the Lancaster transform be adopted as the community standard for reducing disparity between results reported as MNI or Talairach coordinates, and suggest that future spatial normalization strategies be designed to minimize this variability in the literature.
Magnetic resonance imaging (MRI) has been proposed as a source of information for automatic prediction of individual diagnostic in schizophrenia. Optimal integration of data from different MRI ...modalities is an active area of research aimed at increasing diagnostic accuracy. Based on a sample of 96 patients with schizophrenia and a matched sample of 115 healthy controls that had undergone a single multimodal MRI session we generated individual brain maps of grey matter vbm, 1back and 2back levels of activation (nback fMRI), maps of amplitude of low frequency fluctuations (resting fMRI) and maps of weighted global brain connectivity (resting fMRI). Four unimodal classifiers (Ridge, Lasso, Random Forests and Gradient boosting) were applied to these maps to evaluate their classification accuracies. Based on the assignments made by the algorithms on test individuals we quantified the amount of predictive information shared between maps (what we call redundancy analysis). Finally, we explored the added accuracy provided by a set of multimodal strategies that included post-classification integration based on probabilities, two step sequential integration and voxel level multimodal integration through 1D-convolutional neural networks (1D-CNN). All four unimodal classifiers showed the highest test accuracies with the 2back maps (80% on average) achieving a maximum of 84% with the Lasso. Redundancy levels between brain maps were generally low (overall mean redundancy score of 0.14 in a 0-1 range) indicating that each brain map contained differential predictive information. The highest multimodal accuracy was delivered by the two step Ridge classifier (87%) followed by the Ridge maximum and mean probability classifiers (both with 85% accuracy) and by the 1D-CNN that achieved the same accuracy than the best unimodal classifier (84%). From the results we conclude that from all MRI modalities evaluated, task based fMRI may be the best option for unimodal diagnostic in schizophrenia. Low redundancy values point to ample potential for accuracy improvements through multimodal integration, with the two step Ridge being a suitable strategy.
Impaired cognitive function has been identified as a core feature of schizophrenia. However, a significant proportion of patients do not show any cognitive deficits. The aim of this study was to ...assess if there were differences in white matter integrity between patients with and without cognitive impairment.
A diffusion tensor imaging study and neurocognitive assessment were conducted in 49 patients with first-episode psychosis and 41 healthy comparison subjects. Subjects were assessed using the Continuous Performance Test, the Grooved Pegboard Test, the Rey Auditory Verbal Learning Test, and the Trail Making Test Part B. For each test, the patient sample was subdivided according to performance, with those scoring more than one standard deviation below the normative mean categorized as impaired. For each cognitive domain, white matter fractional anisotropy in deficit and nondeficit subgroups was compared using a voxel-based analysis. A nonparametric statistical method, controlling for multiple comparisons, was applied.
Impairment on the Trail Making Test Part B was associated with reduced fractional anisotropy in the right/left anterior thalamic radiation and inferior fronto-occipital fasciculus, forceps minor, and left superior and inferior longitudinal fasciculi. Patients exhibiting Grooved Pegboard Test impairment showed reduced fractional anisotropy in the forceps minor, inferior fronto-occipital fasciculus, anterior thalamic radiation, and corticospinal and corticopontine tracts. Impaired performance on the Rey Auditory Verbal Learning Test and Continuous Performance Test was not associated with significant differences in fractional anisotropy.
Deficits in executive and motor functioning in patients with first-episode psychosis are associated with reductions in white matter integrity in the major fasciculi that connect the frontal and temporal cortices as well as in pathways connecting cortical and subcortical regions. Their presence at the onset of illness, in minimally medicated patients, indicates that these findings are not attributable to effects of chronic illness or its treatment.
Disruptions in white matter structure have consistently been shown in schizophrenia — but mainly in patients in whom the illness is well-established. In order to determine whether white matter ...abnormalities are present at illness onset, and to minimise the potentially confounding effects of chronic illness and treatment, we used diffusion tensor imaging to study a large cohort of first episode psychotic patients who were medication-naive.
Sixty two first episode patients and 54 controls matched on age, sex, years of education and laterality index underwent diffusion tensor imaging. Data were acquired on a GE Signa NVi 1.5 Tesla System. Fractional anisotropy maps were generated on a voxel-by-voxel basis. An optimized voxel-based morphometry technique was conducted with two-stage registration approach. Group differences were examined using a non-parametric statistical method.
The voxelwise analysis revealed four clusters where fractional anisotropy values were significantly lower in patients than controls. These were localised bilaterally to regions of white matter corresponding to superior and inferior longitudinal fasciculus, forceps major, anterior and superior thalamic radiation and corpus callosum.
Reductions in white matter integrity are present early in the course of the schizophrenia and localised in fascicule that connect brain regions implicated in the disorder.
To evaluate a wide range of optical coherence tomography (OCT) parameters for possible application as a screening tool for cognitively healthy individuals at risk of Alzheimer's disease (AD), ...assessing the potential relationship with established cerebrospinal fluid (CSF) core AD biomarkers and magnetic resonance imaging (MRI).
We studied 99 participants from the Valdecilla Study for Memory and Brain Aging. This is a prospective cohort for multimodal biomarker discovery and validation that includes participants older than 55 years without dementia. Participants received a comprehensive neuropsychological battery and underwent structural 3-T brain MRI, lumbar puncture for CSF biomarkers (phosphorylated-181-Tau (pTau), total Tau (tTau), beta-amyloid 1-42 (Aβ 1-42), and beta-amyloid 1-40 (Aβ 1-40)). All individuals underwent OCT to measure the retinal ganglion cell layer (GCL), the retinal nerve fiber layer (RFNL), the Bruch's membrane opening-minimum rim width (BMO-MRW), and choroidal thickness (CT). In the first stage, we performed a univariate analysis, using Student's t-test. In the second stage, we performed a multivariate analysis including only those OCT parameters that discriminated at a nominal level, between positive/negative biomarkers in stage 1.
We found significant differences between the OCT measurements of pTau- and tTau-positive individuals compared with those who were negative for these markers, most notably that the GCL and the RNFL were thinner in the former. In stage 2, our dependent variables were the quantitative values of CSF markers and the hippocampal volume. The Aβ 1-42/40 ratio did not show a significant correlation with OCT measurements while the associations between pTau and tTau with GCL were statistically significant, especially in the temporal region of the macula. Besides, the multivariate analysis showed a significant correlation between hippocampal volume with GCL and RNFL. However, after false discovery rate correction, only the associations with hippocampal volume remained significant.
We found a significant correlation between Tau (pTau) and neurodegeneration biomarkers (tTau and hippocampus volume) with GCL degeneration and, to a lesser degree, with damage in RFNL. OCT analysis constitutes a non-invasive and unexpensive biomarker that allows the detection of neurodegeneration in cognitively asymptomatic individuals.
Cortical thickness has been widely studied in individuals with schizophrenia and, in particular, first-episode psychosis. Abnormalities have been described, although there is, to date, a lack of ...consensus regarding changes across time and correlations with clinical and functional outcomes of the illness.
One hundred and twenty-three first-episode psychosis patients and 74 healthy volunteers were subjected to magnetic resonance imaging scans and clinical and functional assessments by different scales at four consecutive visits during a 10 year follow-up period. Linear mixed effects models were applied to our data to compute cortical thickness changes over time in (1) schizophrenia patients versus healthy controls and (2) in patients with good versus poor functional outcome. The associations between cortical thickness percentage changes and clinical and functional status at 10 years were also assessed.
The patients presented a thinner cortex than the controls at baseline (b's = −0.06; q ≤ 0.00023) with non-significant coefficients for the interaction term (follow-up time x group) (b's = −0.001; q ≥ 0.681). Poor functioning patients presented statistically significant coefficients for the interaction term (follow-up time x functionality) (left: b = −0.005, q = 0.019; right: b = −0.005, q = 0.022). In contrast, no correlations were found between cortical thickness measurements and clinical variables at 10 years.
Overall, there were widespread thickness anomalies in first-episode psychosis patients across cortical regions that remained stable across time. Progressive thickness changes were related to patient functional outcomes, with progressive and steeper cortical thinning in patients with worse functional outcomes and a stabilization in those with better outcomes.
Lack of insight is a core feature of non-affective psychosis and has been associated with poorer outcomes. Brain abnormalities underlying lack of insight have been suggested, mostly in the frontal ...lobe, although previous research showed mixed results. We used a voxel-based morphometry (VBM) analysis in 108 first-episode non-affective psychosis patients to investigate the pattern of brain structural abnormalities related to lack of insight. In addition, 77 healthy volunteers were compared with the patients classified as having poor and good insight. The shortened version of the Scale to Assess Unawareness of Mental Disorder was used to evaluate insight. Patients with poor insight (n = 68) compared with patients with good insight (n = 40) showed a single significant cluster (kc = 5834; PcFWE = 0.001) of reduced grey matter volume (GMV) in the right occipital lobe extending to its lateral and medial surfaces, the cuneus, and the middle temporal gyrus. In addition, GMV at this cluster showed a negative correlation with the score of the SUMD (r = -0.305; p = 0.001). When comparing patients with poor insight with healthy subjects overall reductions of GMV were found, mainly in frontal and occipital lobes. Hence, poor insight in non-affective psychosis seems to be associated with specific brain abnormalities in the right occipital and temporal cortical regions. Dysfunction in any combination of these areas may contribute to lack of insight in non-affective psychosis. Specifically, the 'right' hemisphere dysfunction underlying impaired insight in our sample is consistent with previously reported similarities between lack of insight in psychosis and anosognosia in neurological disorders.
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